In recent years, advancement made in biotechnologies has developed various new methods for detecting breath metabolites that are related to diseases. These new developments in technologies have made possible direct and fast responding techniques for detection. For instance, in a co-pending application assigned to the common assignee of the present application, Attorney Docket No. 64,600-024 which incorporated hereby in its entirety by reference, a system and method for modeling peptides to cover an artificial nose have been proposed. The artificial nose equipped with sensing films can be used to detect various forms of human diseases by detecting specific chemical species of exhaled gases that are associated with such diseases. In most circumstances, in order to detect a certain physical condition or a disease, a number of chemical species must be detected. Since the peptides developed to cover an artificial nose can be used to identify only one type of gas molecules associated with a certain smell, a number of artificial nose that are packaged in separate sensing elements must be used to accommodate the different peptides required for sensing the various types of gas molecules. In order to put the artificial nose to practical use, the various sensing films containing peptides as a cover for an artificial nose must be packaged together in a single unit so that it can be used to monitor and detect the various gases simultaneously. When the use of such a detection unit is mobile, the unit should be designed in a compact size so that it can be moved and carried easily. The packaging of a multiple number of sensing elements in a small and compact unit is therefore an important aspect of the technology that must be developed before it can be put to practical use.
In packaging a number of sensing elements, or chips, into a small and compact unit, conventional technology used for packaging microelectronic IC chips into a so-called multi-chip module is first considered. However, the multi-chip modules developed in the semiconductor industry requires the multiple number of IC chips be encapsulated completely and therefore sealed in an insulative material. This makes it impossible for the detection of gas molecules by the sensing elements since the elements would be encapsulated in a solid insulative material such as a polymer. The conventional multi-chip module used in the semiconductor industry therefore does not provide a package that leaves an access to the sensing elements. Furthermore, since the detection of specific gas molecules associated with a biological condition requires extremely high sensitivity in order to detect a minute amount of the gas, the effect of any noise signals produced by a poorly designed package is detrimental to the proper functioning of the sensing elements. The conventional multi-chip modules are not designed for minimizing noise signals, specifically at its output terminals. A new method for packaging which minimizes noise signals produced either inside the package or at the output terminals must be provided before the package can be reliably used in biomedical type of detections.
It is therefore an object of the present invention to provide a method for forming a multi-chip sensing device that does not have the drawbacks or shortcomings of the conventional methods.
It is another object of the present invention to provide a method for forming a multi-chip sensing device that is equipped with an open front such that the sensing elements may detect gas molecules that the devices are exposed to.
It is a further object of the present invention to provide a multi-chip sensing device wherein noise signals generated at the output terminals of the device is minimized.
It is another further object of the present invention to provide a method for forming a multi-chip sensing device that is capable of accommodating a multiple number of sensing elements in a compact package.
It is still another object of the present invention to provide a multi-chip sensing device by mounting a multiple number of sensing elements to an electrically insulative substrate.
It is yet another object of the present invention to provide a multi-chip sensing device by providing a plurality of bonding sites on a ceramic substrate wherein each site includes at least two interconnection pads and two signal output pads formed of an electrically conductive metal.
It is still another further object of the present invention to provide a method for fabricating a multi-chip sensing device by forming interconnection pads and signal output pads on a ceramic substrate by a thick film printing technique.
It is yet another further object of the present invention to provide a method for fabricating a multi-chip sensing device by bonding a multiple number of sensing elements to a multiple number of bonding sites built on a ceramic substrate by a solder containing Sn and Pb.